Toulouse 2002

Dunedin

LytteltonWellington

Auckland

Correcting New ZealandCorrecting New Zealand’s’s long- long-term sea level records for term sea level records for

tectonictectonic upliftuplift uusingsing continuous GPS continuous GPS

observationsobservations

Paul DenysPaul Denys

John BeavanJohn Beavan

Dion MathesonDion Matheson

Mikael DenhamMikael Denham

Chris PearsonChris Pearson

John HannahJohn Hannah

Toulouse 2002

Paired CGPS and CGPS@TG sitesPaired CGPS and CGPS@TG sites

• Sites with ~100 Sites with ~100 years of TG years of TG recordsrecords

• CGPS close or CGPS close or collocated with TG collocated with TG recordersrecorders

• But … Problems … But … Problems … • TG sites not stableTG sites not stable• Possible GPS Possible GPS

masking problemsmasking problems• High multipath High multipath

environmentsenvironments

• Requires careful Requires careful monitoringmonitoring

AUCK & TAKL

WGTN & WGTT

MQZG & LYTT

OUSD & DUNT

Toulouse 2002

Tide Gauge Site Stability Monitoring Tide Gauge Site Stability Monitoring

• Local stability:Local stability: TG pole/recorder to local benchmarksTG pole/recorder to local benchmarks• Regional stability:Regional stability: CGPS@TG to regional CGPSCGPS@TG to regional CGPS

CGPS to CGPS@TG

(km)

TG to CGPS@TG

(km)

CGPS@TG to TGConnection

Method

AucklandAuckland 27.327.3 CollocatedCollocated Spirit levelSpirit level

WellingtoWellingtonn

4.24.2 0.550.55 Spirit level + Spirit level + GPSGPS

LytteltonLyttelton 12.112.1 CollocatedCollocated Spirit levelSpirit level

DunedinDunedin 11.111.1 0.40.4 Spirit levelSpirit level

Toulouse 2002

Ports of Ports of Auckland Auckland

Tide Gauge Tide Gauge and TAKL and TAKL

CGPS StationCGPS Station

• Located on Captain Cook Located on Captain Cook Wharf, AucklandWharf, Auckland

• Tide gauge measurement Tide gauge measurement system uses microwaves system uses microwaves reflected off sea surface reflected off sea surface beneath wharfbeneath wharf

• Reference surface of tide Reference surface of tide gauge is immediately gauge is immediately adjacent to base of GPS adjacent to base of GPS antennaantenna

Tide Gauge mountedunder this cover

CGPSantenna(TAKL)

Base of antenna mast firmly

bolted to wharf

Toulouse 2002

GPS receiver

Industrial PCon internet

Power Supply/ Battery charger

Back-up battery

CGPS Receiver at Ports of AucklandCGPS Receiver at Ports of Auckland

Toulouse 2002

Automatic tide gauge Manual gauge

Measuring system at Wellington float-type tide Measuring system at Wellington float-type tide gaugegauge

Toulouse 2002

WGTT Continuous GPS WGTT Continuous GPS StationStation

Mast is attached

through facing onto the mainstructural wall of the museum

Toulouse 2002

Toulouse 2002

• Install Temporary GPS (WGTA)

• 50 m from TGBM for 24 hours every 3 months

• Same antenna type and radome used at WGTT and WGTA

• Level TGBM and WGTA several times during 24 hour period

• GPS Baseline Processing

• Troposphere variation solved at WGTT as part of regional network processing

• Same troposphere variation assumed at WGTA as at WGTT when solving for the WGTT - WGTA height difference

• Another CGPS site, WGTN, is located in bedrock 5.5 km from WGTT

• Provides a check on the stability of WGTT

HEIGHT CONNECTION from WELLINGTON TIDE GAUGE BENCH MARK (TGBM) to CONTINUOUS GPS (WGTT)

Toulouse 2002

Location of WGTT CGPS (at Te Papa)

Temporary GPS used to tie between tide gauge BM and WGTT

GPS levelling: temporary GPS to WGTT CGPSGPS levelling: temporary GPS to WGTT CGPS

Toulouse 2002

Temporary GPS used to tie between tide gauge BMand WGTT

Precise levelling: Wellington tide gauge to Precise levelling: Wellington tide gauge to temporary GPStemporary GPS

Level

Toulouse 2002

Precise and GPS levelling results: Wellington Precise and GPS levelling results: Wellington tide gaugetide gauge

Toulouse 2002

Combined geodetic and GPS levelling resultsCombined geodetic and GPS levelling resultsWellington tide gaugeWellington tide gauge

Toulouse 2002

Structure Stability Problems: Wooden Wharf Structure Stability Problems: Wooden Wharf at Lytteltonat Lyttelton

Tide Gauge Hut and and GPS antenna

-60 -40 -20 0 20 40 60-60

-40

-20

0

20

40

60

Longitude (mm)

La

titu

de

(m

m)

Velocity 44.2mm/yr

Toulouse 2002

CGPS@TG site

TG recorder and tide pole

Port Chalmers: Poor GPS EnvironmentPort Chalmers: Poor GPS Environment

Toulouse 2002

Regional Stability: CGPS to CGPS@TGRegional Stability: CGPS to CGPS@TG

2000 2000.5 2001 2001.5 2002 2002.5

-20

0

20

40

60

80

100

120

140

160

OUSD-DUNT Vel: -0.6mm/yr rms: +/- 5.9mm

MQZG-LYTT Vel: -0.7mm/yr rms: +/- 4.5mm

WGTN-WGTT Vel: -1.2mm/yr rms: +/- 5.7mm

AUCK-TAKL Vel: +8.8mm/yr rms: +/- 6.9mm

Time (Years)

He

igh

t R

es

idu

al (

mm

)

Baseline Height Component

Toulouse 2002

rms of Baseline Components and Vertical rms of Baseline Components and Vertical VelocityVelocity

BaselinBaseline e

DistancDistance (km)e (km)

LatitudLatitude (mm)e (mm)

Longitide Longitide (mm)(mm)

Height Height (mm)(mm)

Velocity Velocity (mm/yr)(mm/yr)

OUSD-OUSD-DUNTDUNT

11.1 1.9 1.8 5.9 0.6

MQZG-MQZG-LYTTLYTT

12.1 4.6 2.5 4.5 0.7

WGTN-WGTN-WGTTWGTT

4.2 2.4 3.6 5.7 1.2

AUCK-AUCK-TAKLTAKL

27.3 1.6 1.8 6.9 8.8

Toulouse 2002

Tide Gauge Mean Annual Sea Level Record: Tide Gauge Mean Annual Sea Level Record: June 2002June 2002

SeaLevelSeaLeveltruetrue = SeaLevel = SeaLevelmeasuredmeasured +/- ??? +/- ???

1900 1920 1940 1960 1980 2000

1.8

2

2.2 AUCK Vel: +1.3 mm/yr rms: +/- 32.8 mm

1900 1920 1940 1960 1980 20000.4

0.6

0.8

1

Me

an

Se

a L

ev

el (

me

tre

s)

WGTN Vel: +2.1 mm/yr rms: +/- 38.5 mm

1900 1920 1940 1960 1980 2000

0.8

1

1.2

Time (Years)

LYTT Vel: +2.0 mm/yr rms: +/- 33.0 mm

??? OBSERVEDTRUE LevelSeaLevelSea

Toulouse 2002

New Zealand’s CGPS @TG New Zealand’s CGPS @TG ProjectProject

• CGPS installed at 4 CGPS installed at 4 long record TG long record TG locations locations

• CGPS collocated or CGPS collocated or within 600mwithin 600m

• Site stability monitored Site stability monitored using a variety of using a variety of methodsmethods• Precise levelling to close Precise levelling to close

BMsBMs• GPS “levelling” to GPS “levelling” to

regional CGPS and TG regional CGPS and TG BMBM

• CGPS to CGPS @TG CGPS to CGPS @TG stabilitystability

• Baselines 4, 11, 12 & Baselines 4, 11, 12 & 27km27km

• Horz rms Horz rms 2-3mm2-3mm(excluding MQZG-LYTT)(excluding MQZG-LYTT)

• Vert rms Vert rms 5-7mm5-7mm

• Vert vel ~1mm/yr Vert vel ~1mm/yr (excluding AUCK-TAKL)(excluding AUCK-TAKL)